question about do_IRQ + 4k stacks

From: Terence Ripperda (tripperda_at_nvidia.com)
Date: 03/31/05

  • Next message: Pau Aliagas: "Re: i386/x86_64 segment register issuses (Re: PATCH: Fix x86 segment register access)" 
    Date:	Wed, 30 Mar 2005 16:10:42 -0600
To: Linux Kernel Mailing List <linux-kernel@vger.kernel.org>

    I'm investigating some 4k stack issues with our driver, and I noticed
    this ordering in do_IRQ:

    asmlinkage unsigned int do_IRQ(struct pt_regs regs)
    {
            ...

    #ifdef CONFIG_DEBUG_STACKOVERFLOW
            /* Debugging check for stack overflow: is there less than 1KB free? */
            {
            ...
            }
    #endif

            ...

    #ifdef CONFIG_4KSTACKS

            for (;;) {
            ... switch to interrupt stack
            }
    #endif

    Is the intention of this stack overflow check to catch a currently
    running kernel thread that's getting low on stack space, or is the
    intent to make sure there's enough stack space to handle the incoming
    interrupt? if the later, wouldn't you want to potentially switch to
    your interrupt stack to be more accurate? (I recognize that often you
    will have switched to an empty stack, unless you have nested
    interrupts)

    Thanks,
    Terence

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